Magnetic trip structures are designed to respond to a current overload detected in a circuit breaker. Typically, an electromagnet provides a magnetic field in response to the current flowing through the breaker. When the current level increases beyond a predetermined threshold, the magnetic field increases to a level which is sufficient to attract an armature toward the electromagnet. The armature is biased away from the electromagnet in its normal, untripped state using a combination of springs, clamps and/or friction bearing devices. In known structures, movement of the armature toward the electromagnet and away from a coupling mechanism causes the coupling mechanism to release circuit breaker contacts, thereby "breaking" the circuit.
The manufacture of such electromagnetic trip structures has been cumbersome and labor intensive. This is primarily due to the many intricate parts that must be assembled in the structures. Manipulation of these many parts is made significantly more difficult by the manner in which they are interconnected. For example, fasteners such as locking pins, rivets, brackets, and costly threaded couplings are commonly used. Unfortunately, the labor that is required due to both the number of parts and their interconnections cannot be tolerated for many cost conscious applications.
This problem is aggravated by post-manufacture maintenance. Maintenance is usually required due to wear and tear of the many parts as well as due to the collection of debris and particles within those parts. A particular type of particle, molten metal which becomes solidified, is often found in a circuit breaker after a current overload is experienced by metallic conductors within the breaker. The molten metal emanates from the metal which carries the overload current. This type of particle has become lodged in known electromagnetic trip structures, causing the structures to jam. Ensuing damage typically includes, at a minimum, damage to appliances powered through the breaker and damage to the circuit breaker itself.